Phase grating image sensing device and method of manufacture

Abstract

A phase grating image-sensing device. The device includes a plurality of photodiodes, a smoothing layer, a color filter layer and a plurality of phase gratings. The photodiodes are formed on a substrate and isolated from each other by isolation structures. The smoothing layer covers the photodiodes and the isolation structures. The color filter layer is embedded within the smoothing layer forming a sandwich structure with the smoothing layer. The phase gratings are formed over the smoothing layer positioned at corresponding locations above isolation structures. The phase grating layers produce a constructive interference of light passing through the smoothing layer.

What is claimed is:  
     
       1. A phase grating imaging sensor, comprising: 
       a plurality of photodiodes on a substrate;  
       an isolation structure between every pair of neighboring photodiodes to isolate the photodiodes from each other;  
       a smoothing layer over the photodiodes and the isolation structures;  
       a color filter layer embedded within the smoothing layer and forming a sandwiched structure; and  
       a plurality of phase gratings on a surface of the smoothing layer at corresponding locations relative to the isolation structures, wherein the phase gratings cause a constructive interference of light passing through the smoothing layer.  
     
     
       2. The imaging sensor of  claim 1 , wherein the phase gratings are positioned on the surface of the smoothing layer at corresponding locations relative to the isolation structures surrounding a periphery of the photodiodes. 
     
     
       3. The imaging sensor of  claim 2 , wherein each phase grating comprises a pattern of concentric rings that surrounds the periphery of the photodiode. 
     
     
       4. The imaging sensor of  claim 3 , wherein the phase gratings are made of a metal. 
     
     
       5. The imaging sensor of  claim 4 , wherein the phase gratings are made of chromium. 
     
     
       6. The imaging sensor of  claim 1 , wherein the phase gratings are made of a metal. 
     
     
       7. The imaging sensor of  claim 6 , wherein the phase gratings are made of chromium. 
     
     
       8. The imaging sensor of  claim 1 , wherein a smoothing layer material is selected from a group consisting of silicon oxide and phosphosilicate glass. 
     
     
       9. The imaging sensor of  claim 1 , wherein the smoothing layer further includes: 
       a first smoothing layer that covers the photodiodes and the isolation structures in contact with one surface of the color filter layer; and  
       a second smoothing layer that covers another surface of the color filter layer.  
     
     
       10. A phase grating imaging sensor, comprising: 
       a plurality of photodiodes on a substrate;  
       an isolation structure between every pair of neighboring photodiodes to isolate the photodiodes from each other;  
       a smoothing layer over the photodiodes and the isolation structures;  
       a color filter layer over the smoothing layer; and  
       a plurality of phase gratings within a surface of the smoothing layer at corresponding locations relative to the isolation structures, wherein the phase gratings cause a constructive interference of light passing through the color filter layer.  
     
     
       11. The imaging sensor of  claim 10 , wherein the phase gratings are positioned within the smoothing layer at corresponding locations relative to the isolation structures surrounding a periphery of the photodiodes. 
     
     
       12. The imaging sensor of  claim 11 , wherein each phase grating comprises a pattern of concentric rings that surrounds the periphery of the photodiode. 
     
     
       13. The imaging sensor of  claim 12 , wherein the phase gratings are made of a metal. 
     
     
       14. The imaging sensor of  claim 13 , wherein the phase gratings are made of chromium. 
     
     
       15. The imaging sensor of  claim 10 , wherein the phase gratings are made of a metal. 
     
     
       16. The imaging sensor of  claim 15 , wherein the phase gratings are made of chromium. 
     
     
       17. The imaging sensor of  claim 10 , wherein a smoothing layer material is selected from a group consisting of silicon oxide and phosphosilicate glass. 
     
     
       18. A method of forming a phase grating image-sensing device, comprising: 
       forming a plurality of photodiodes on a substrate;  
       forming an isolation structure between neighboring photodiodes to isolate the photodiodes from each other;  
       forming a first smoothing layer over the photodiodes and the isolation structures;  
       forming a color filter layer over the first smoothing layer;  
       forming a second smoothing layer over the color filter layer;  
       forming a phase grating layer over the second smoothing layer; and  
       patterning the phase grating layer to form a plurality of phase gratings, wherein the phase gratings cause a constructive interference of light passing through the color filter layer.  
     
     
       19. The method of  claim 18 , wherein patterning the phase grating layer includes conducting a photolithographic and an etching process to form phase gratings at locations corresponding to the isolation structures and encircling a periphery of the photodiodes. 
     
     
       20. The method of  claim 19 , wherein the phase grating layer is patterned into a plurality of phase grating having a concentric pattern around each photodiode. 
     
     
       21. The method of  claim 18 , wherein the phase grating layer is made of a metal. 
     
     
       22. The method of  claim 21 , wherein the phase grating layer is made of chromium. 
     
     
       23. A method of forming a phase grating image-sensing device, comprising: 
       forming a plurality of photodiodes on a substrate;  
       forming an isolation structure between neighboring photodiodes to isolate the photodiodes from each other;  
       forming a first smoothing layer over the photodiodes and the isolation structures;  
       forming a phase grating layer over the first smoothing layer;  
       patterning the phase grating layer to form a plurality of phase gratings;  
       forming a second smoothing layer over the first smoothing layer so that the phase gratings are covered; and  
       forming a color filter layer over the second smoothing layer, wherein the phase gratings cause a constructive interference of light passing through the color filer layer.  
     
     
       24. The method of  claim 23 , wherein patterning the phase grating layer includes conducting a photolithographic and an etching process to form phase gratings at locations corresponding to the isolation structures and encircling a periphery of the photodiodes. 
     
     
       25. The method of  claim 24 , wherein the phase grating layer is patterned into a plurality of phase grating having a concentric pattern around each photodiode. 
     
     
       26. The method of  claim 23 , wherein the phase grating layer is made of a metal. 
     
     
       27. The method of  claim 26 , wherein phase grating layer is made of chromium.